SWIPT in Mixed Near- and Far-Field Channels: Joint Beam Scheduling and Power Allocation

TL;DR

This paper explores joint beam scheduling and power allocation for SWIPT in mixed near- and far-field channels using XL-array technology, optimizing energy harvesting and data transmission.

Contribution

It introduces a new mixed near- and far-field SWIPT scenario and proposes an efficient algorithm for joint beam scheduling and power allocation, including insights for special cases.

Findings

Proposed an algorithm for joint beam scheduling and power allocation.

Showed that in mixed scenarios, power is often allocated to both EH and ID receivers.

Numerical results demonstrate significant performance improvements over benchmarks.

Abstract

Extremely large-scale array (XL-array) has emerged as a promising technology to enhance the spectrum efficiency and spatial resolution in future wireless networks by exploiting massive number of antennas for generating pencil-like beamforming. This also leads to a fundamental paradigm shift from conventional far-field communications towards the new near-field communications. In contrast to the existing works that mostly considered simultaneous wireless information and power transfer (SWIPT) in the far field, we consider in this paper a new and practical scenario, called mixed near- and far-field SWIPT, where energy harvesting (EH) and information decoding (ID) receivers are located in the near- and far-field regions of the XL-array base station (BS), respectively. Specifically, we formulate an optimization problem to maximize the weighted sum-power harvested at all EH receivers by jointly designing the BS beam scheduling and power allocation, under the constraints on the maximum sum-rate and BS transmit power. First, for the general case with multiple EH and ID receivers, we propose an efficient algorithm to obtain a suboptimal solution by utilizing the binary variable elimination and successive convex approximation methods. To obtain useful insights, we then study the joint design for special cases. In particular, we show that when there are multiple EH receivers and one ID receiver, in most cases, the optimal design is allocating a portion of power to the ID receiver for satisfying the rate constraint, while the remaining power is allocated to one EH receiver with the highest EH capability. This is in sharp contrast to the conventional far-field SWIPT case, for which all powers should be allocated to ID receivers. Numerical results show that our proposed joint design significantly outperforms other benchmark schemes without the optimization of beam scheduling and/or power allocation.